Rotary actuators are used as part of some mechanical devices, to deliver rotary motion in an efficient manner. Rotary actuators are desirable because they maintain constant torque and conserve space. Such prior art rotary actuators typically include multiple subcomponents such as a rotor and two or more stator housing components.
Variable geometry on aircraft engines can be positioned by rotary actuators that use jet fuel as the working fluid. The on-engine environment can be very hot. Actuators used in such applications can have cooling orifices that allow a limited flow of fuel through the actuator and the flow of fuel can remove heat, lowering the actuator temperature. Relatively larger fluid pumps, with their associated higher weights and costs, can be implemented to provide such cooling flow, and such cooling flow can contribute to sluggish and/or imprecise position control.